Heat pumps are meant to be boring. Not in the sense of unimportant, but in the way central heating has always worked best when it fades into the background. You set the temperature, the house stays warm, the bills are predictable and life moves on.
Yet speak to enough UK homeowners and a different picture emerges. Some households report winter running costs so low they barely think about them. Others, sometimes in similar homes on the same street, find themselves staring at daily electricity costs that feel wildly out of step with the promise they were sold.
The usual explanations come thick and fast. Poor insulation. User error. Unrealistic expectations. All of them can be true, and often are. But they also serve a useful function: they keep attention away from the systems themselves, and from the uncomfortable variability in how they perform once they leave the showroom.
That variability is what the Havenwise data begins to expose.
Across 2025, Havenwise collected real-world operational data from hundreds of UK heat pumps, all running under the same optimisation strategy. This is not lab testing and it isn’t cherry-picked installs designed to flatter a particular brand. It is messy, domestic reality: different homes, different occupants, real weather, real tariffs, real habits.
When you strip the marketing away and look at how these systems behave day after day, electricity consumption on its own quickly proves to be a dead end. A system drawing very little power can still be performing poorly if it isn’t producing much usable heat. Equally, higher consumption figures are not automatically a sign of failure if they are paired with strong heat output.
This is where Seasonal Coefficient of Performance matters and where much of the public conversation falls apart. SCoP is not a headline number you glance at once and forget. It is the difference between a system that delivers value over a winter and one that erodes trust every time the smart meter updates.
The data also shows just how sensitive outcomes are to winter behaviour, hot water production and flow temperatures. Small shifts in how a system is configured or how it responds to cold snaps, can compound over months into significant cost differences. These are interactions most homeowners are never properly briefed on, yet they dominate real-world performance.
Perhaps most revealing, though, is that the story is not only about hardware.
When comparing systems from Vaillant, Mitsubishi and Samsung, the numbers themselves tell only part of the tale. Data quality varies. Reporting consistency varies. In some cases, the data is clean enough to draw confident conclusions. In others, gaps and ambiguities make interpretation harder, even when the underlying performance may be sound.
This is important because a heat pump does not exist in isolation. It sits inside a wider ecosystem: controls, monitoring tools, manufacturer support and the willingness to surface inconvenient truths when performance drifts. A technically capable unit paired with weak data transparency leaves both homeowners and installers effectively flying blind.
The Havenwise findings also align closely with years of lived experience shared on the Renewable Heating Hub forums. Patterns repeat. Certain frustrations recur. So do certain successes. When data and anecdote converge, it becomes harder to dismiss either as noise.
This is not a verdict on which logo belongs on your wall. It is not a ranking table and it is certainly not a sponsored shoot-out. What it does show, rather clearly, is that outcomes in the heat pump market are still far less predictable than they should be and that brand reputation alone is a poor proxy for real-world performance.
For homeowners already living with a heat pump, understanding this data can be reassuring or unsettling, sometimes both. It can confirm that a system is behaving as expected, or highlight inefficiencies that were previously written off as “just how heat pumps are”.
For those considering an installation, it serves as a reminder that the most important questions are rarely answered in brochures. How does this system behave in winter? What data will I actually see? And if something looks wrong, how quickly can I prove it?
Once the installer leaves and the marketing stops, those questions are what determine whether a heat pump becomes a background utility, or a daily source of doubt.
At last, some real information on the performance of ASHP’s. Thank you.
Where can I view the actual daata?